QUICK FACTS
Where is it? Central Java, Indonesia [-7.34485373, 110.02748950]
What’s in the photo? Mount Sundoro (left) and Mount Sumbing (right)
Who took the photo? An unnamed astronaut on board the International Space Station
When was it taken? May 10, 2021
This awesome astronaut photo shows the striking symmetry of “twin” stratovolcanoes at the heart of Java, Indonesia. The parallel peaks are an eye-catching reminder of the region’s extreme tectonic activity.
Mount Sundoro (also known as Sindoro or Sindara) on the left of the image, reaches a maximum height of 10,331 feet (3,149 meters). Its partner, Mount Sumbing, sits to the southeast (on the right of the image) and is slightly taller, at 11,056 feet (3,370 m) above sea level.
Both are considered active. Although Sumbing has not erupted since 1730, Sundoro has blown its top more recently, in 1971, and has experienced seismic activity as recently as 2012, according to the Smithsonian Institution’s Global Volcanism Program.
The volcanoes’ peaks are just 7.5 miles (12 kilometers) apart. A raised ridge with a major highway runs perpendicularly between them.
Each volcano also has a smaller, secondary cone on its flank left over from previous eruptions (to the upper left of Sundoro and the upper right of Sumbing in the image), and their orientations make the volcanoes look like mirror images of each other.
The two volcanoes also have strikingly similar profiles when viewed from ground level.
(Image credit: Rizky Panuntun via Getty Images)
The slopes of both cones are covered with rings of dark-green forest that sharply terminate at their bases. The volcanic soils surrounding the mountains are excellent for growing crops such as rice, corn, coffee and sugarcane, which has led to the deforestation of their surroundings, according to NASA’s Earth Observatory.
This matching coloration accentuates the similarities between the pair, especially when viewed from above.
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One of the few differences between Sundoro and Sumbing is that the latter volcano has a sizable crater at its summit, which was carved out by the 1730 eruption. As a result, the larger volcano appears to have a darker point at its top.
The volcanoes are commonly referred to as “twins,” due to their near-identical profiles. However, local people often call them “husband and wife,” according to a local travel site. In this narrative, Sumbing is considered the husband due to its slight height advantage and “more masculine” profile.
The land surrounding Mount Sundoro and Mount Sumbing (photographed) is rich with volcanic ash, making it ideal for growing various crops.
(Image credit: Wikimedia)
Sundoro and Sumbing are part of the wider Dieng Volcanic Complex, which consists of around 20 volcanic cones stretching across central Java. Indonesia is also positioned along the “Ring of Fire,” a roughly horseshoe-shaped arc of volcanoes that runs along a series of tectonic plate boundaries encircling the Pacific Ocean.
Over the past few years, there have been a number of significant eruptions in Indonesia, including a pair of violent blasts at Mount Lewotobi Laki-laki, on Flores Island, in 2024 and 2025. As of June 2026, there are seven ongoing eruptions in Indonesia — the most of any nation.
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